Robert Miller: The one-two punch to hemlocks’ nemesis

Updated 1:42 pm, Tuesday, August 1, 2017

Carole Cheah has crisscrossed Connecticut this year, fighting the good fight to save the state’s hemlocks from the scourge of sap-sucking aphids. Her allies: thousands of lady beetles.

The fight is essential for an evergreen that, growing in dense stands on steep hillsides, can cool a brook for trout, create a wildlife habitat, define a place.

“It creates an aesthetic all its own,” said Ann Astarita, executive director of the Roxbury Land Trust, thinking of the hemlock stand on the trust’s Mine Hill Preserve. “It’s great for hikers.”

And it’s a type of place that’s under siege. A non-native pest — the hemlock wooly adelgid — has been damaging the state’s hemlocks since Hurricane Gloria blew it into the state in 1985.

The adelgid is an aphid that gets its name from the small white egg sacs it lays in the underside of hemlock boughs. The larvae feed on the tree’s sap, injecting it with toxic saliva as well. Give the adelgids a few years and they can decimate a stand of hemlock.

“They were trees growing on ledges where nothing else could grow,” Martin said.

Adelgid damage has slowed, but they’ve spread throughout the state.

“It’s definitely around,” said Paul Elconin, director of land conservation at the Weantinoge Heritage Land Trust, the largest land trust in the state. “You can just turn over the branches and see it. It’s so common.”

But Elconin also speaks of how beautiful the hemlock stands are along the trails in its Eleanor and Henry Hunt Nature Preserve in New Milford.

“It really gives you a dense stand of trees,” he said. “If we’d lose it, it would change the complexity of that place.”

She has also participated in a program that uses biocontrol to kill the adelgids. The experiment station released about 176,000 black lady beetles — Sasajiscymus tsugae — in hemlock stands throughout the state. The beetles are adelgid hunters, killing them and controlling their spread.

The program has been successful. But for a variety of reasons, Cheah hasn’t had the chance to release more beetles for a decade.

Good things happened this year.

While the 2016-17 winter was mild, the three previous ones all had severe cold spells that did a great job of killing the adelgids.

“The most surprising was the winter of 2016,” Cheah said. “People think of it as a mild winter. But we had that killer cold spell in February. It ruined the peach crop in the state, but it killed adelgids.”

Knowing the cold had knocked the aphids on their heels, Cheah contacted Tree Savers, a Pennsylvania-based company that raises the lady beetles for commercial sales. It donated 2,000 beetles to the experiment station and Cheah took them on the road.

She traveled to seven different sites in the state — from Pachaug State Forest in the southeast corner of the state to the Great Mountain Forest in the northwest — finding places where the beetles might work best.

One was at the Mine Hill Preserve in Roxbury.

“I worked with Carole in Newtown releasing weevils to control Mile-a-Minute vines,” Astarita of the Roxbury Land Trust said. “I know she really knows her business. When we found out she was releasing the beetles, we were absolutely interested.”

Monroe Tree Warden Dave Solek said the combination of the winter kills and the new releases of the beetles may help keep the adelgids at bay at the park.

“Anything we can do is good,” Soleck said. “This is a one-two punch.”

Cheah also said this year’s plentiful rain is reviving many hemlocks badly stressed by the drought that began in 2015 and stretched through 2016. That dry weather allowed another insect — the hemlock borer — to damage stressed trees.

While the beetles do their job, Cheah acknowledged that it is the weather, in a time of climate change, that will determine the hemlocks’ fate in the future.

“We don’t know when the polar vortex will move and where it will move to,” she said. “It’s so unpredictable.”